Topsheet for absorbent article

ABSTRACT

A topsheet for absorbent articles having absorbing performance for smoothly transferring liquid body waste, e.g., menstrual blood or urine, to an underlying absorbent member and surface characteristics such that the surface thereof in contact with wearer&#39;s skin is soft enough not to cause skin irritation. The topsheet  1  comprises a first layer  11  disposed on the side of a wearer and a second layer  12  disposed on the side of an absorbent member, the first layer and the second layer being partly joined together, and having protrusions and depressions on the side of a wearer, wherein the first and second layers each comprise a fiber aggregate, the first layer has fusion-bonded fiber intersections, the first layer has an apparent thickness (t1) of 0.1 to 5 mm, the second layer has an apparent thickness (t2) of 0.2 to 3 mm, the apparent thickness ratio of the first layer to the second layer (t1/t2) is 0.5 to 8, the first layer has a fiber density (d1) of 0.001 to 0.05 g/cm 3 , the second layer has a fiber density (d2) of 0.03 to 0.2 g/cm 3 , and the fiber density (d2) of the second layer is higher than that (d1) of the first layer.

FIELD OF THE INVENTION

[0001] The present invention relates to absorbent articles, such assanitary napkins, panty liners, incontinence pads, and disposablediapers, and a sheet which is used in the absorbent articles as atopsheet to be brought into contact with a wearer's body.

BACKGROUND OF THE INVENTION

[0002] Topsheets used in absorbent articles, such as sanitary napkins,are required to have not only absorbing performance for smoothlytransferring liquid body waste, e.g., menstrual blood or urine, to anunderlying absorbent member but surface characteristics such that thesurface thereof in contact with wearer's skin is soft enough not tocause skin irritation.

[0003] Currently available topsheets for absorbent articles includenonwoven fabrics made by various processes, perforated nonwoven fabrics,and perforated films of synthetic resins such as polyethylene, but noneof them sufficiently satisfies the above-mentioned requirements ofabsorbing performance and surface characteristics.

[0004] Absorbent articles having a topsheet made of nonwoven fabric aredisadvantageous in that waste liquid, e.g., menstrual blood or urine,discharged on the topsheet remains in the vicinity of the surface of thetopsheet and gives discomfort or an unsanitary impression to a user onaccount of its color. Absorbent articles having a topsheet made of aperforated film relatively hide the color of blood or urine but areinferior in surface softness to those having a nonwoven fabric topsheet.

[0005] Japanese Patent 3131557 discloses wrinkled nonwoven fabric with agreat number of streaky wrinkles (ridges) arrayed on its surface, whichis used as a topsheet of an absorbent article. However, because of largeempty spaces inside the ridges, liquid discharged on the topsheetpenetrates into the surface of the wrinkles to make its colornoticeable. Besides, this structure is not one that allows the liquid toquickly migrate to the absorbent member, which tends to causeoverhydration.

[0006] Japanese Patent 3181195 discloses nonwoven fabric suitable foruse as a female member of a mechanical fastener of disposable diapers,etc., which is obtained by partly joining a first fiber layer and asecond fiber layer by heat fusion and thermally shrinking one of thefirst and second layers to make the other protrude toward one side toform regularly arrayed bulges. Because the two layers are partly joinedby heat embossing in a very fine pattern, the nonwoven fabric is toohard for use as a topsheet of an absorbent article. Further, the fiberlayer forming the bulges easily fuzzes up because of weak fusion bondsamong constituent fibers. Therefore, if used as the topsheet of theabsorbent article, the nonwoven fabric excessively irritates the skin tocause skin troubles.

[0007] JP-A-10-80445 discloses a topsheet for absorbent articles whichcomprises two nonwoven fabric layers and has a large number of openings,the two nonwoven fabric layers being joined together at the periphery ofthe individual openings. The topsheet disclosed may not be necessarilyseen as sufficiently infiltratable for transferring liquid from thefirst layer (on the wearer's side) to the second layer (on the absorbentmember side).

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide a topsheet forabsorbent articles which exhibits sufficient absorbing performance formaking discharged body liquid such as blood or urine quickly migrate tothe absorbent member and has excellent softness on its side to bebrought into contact with wearer's skin for causing little skinirritation, preventing an itch, a rash or discomfort due tooverhydration or irritation, and giving a wearer comfort.

[0009] Another object of the present invention is to provide anabsorbent article which hides the color of a body liquid such as bloodor urine discharged on the topsheet thereof and thereby gives a sanitaryimpression to a user and has excellent softness on the wearer's side toprevent an itch, a rash or discomfort due to physical irritation, andassures a wearer an excellent comfort (a cushioning feel) while beingworn.

[0010] The first object of the present invention is accomplished by atopsheet for an absorbent article comprising a first layer disposed onthe side of a wearer and a second layer disposed on the side of anabsorbent member, the first layer and the second layer being partlyjoined together, and having protrusions and depressions on the side of awearer, wherein the first and the second layers each comprise a fiberaggregate, the first layer has fusion-bonded fiber intersections, thefirst layer has an apparent thickness (t1) of 0.1 to 5 mm, the secondlayer has an apparent thickness (t2) of 0.2 to 3 mm, the apparentthickness ratio of the first layer to the second layer (t1/t2) is 0.5 to8, the first layer has a fiber density (d1) of 0.001 to 0.05 g/cm³, thesecond layer has a fiber density (d2) of 0.03 to 0.2 g/cm³, and thefiber density (d2) of the second layer is higher than that (d1) of thefirst layer.

[0011] The second object of the present invention is accomplished by anabsorbent article comprising a liquid permeable topsheet, a liquidimpermeable backsheet, and a liquid retentive absorbent memberinterposed between the topsheet and the backsheet, wherein the topsheetcomprises a first layer disposed on the side of a wearer and a secondlayer disposed on the side of an absorbent member and has protrusionsand depressions on the side of a wearer, the first layer comprises afiber aggregate having fusion-bonded fiber intersections, the firstlayer has an apparent thickness (t1) of 0.1 to 5 mm, the second layerhas an apparent thickness (t2) of 0.2 to 3 mm, the apparent thicknessratio of the first layer to the second layer (t1/t2) is 0.5 to 8, thetopsheet shows a through-thickness deformation of 0.03 to 0.3 mm pergf/cm² when compressed under a load of 10 gf/cm², and the topsheet has asurface whiteness (L value) of 60 or higher and a red plate hiding ratioof 40% or higher.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be more particularly described withreference to the accompanying drawings, in which:

[0013]FIG. 1 is an exaggerated cross-sectional view of a topsheetaccording to the present invention, designed for use in a sanitarynapkin;

[0014]FIG. 2 shows the steps involved in the production of the topsheetshown in FIG. 1;

[0015]FIG. 3 is a plan of a sanitary napkin as an embodiment of theabsorbent article according to the present invention, in which thetopsheet of FIG. 1 is used;

[0016]FIG. 4 is a cross-sectional view taken along X-X of FIG. 3; and

[0017]FIG. 5A and FIG. 5B each schematically illustrate the method ofmeasurement in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The present invention will be described in greater detail withreference to its preferred embodiments.

[0019] An embodiment of the topsheet according to the present inventionis described first. As shown in FIG. 3, a topsheet 1 according to thisembodiment is used on the side of an absorbent article which is to comeinto contact with a wearer's skin. As shown in FIG. 1, the topsheet 1comprises a first layer 11 disposed on the side of a wearer and a secondlayer 12 disposed on the side of the absorbent member.

[0020] The first layer 11 and the second layer 12 are each made of afiber aggregate and are joined together in parts.

[0021] As shown in FIG. 1, the joints 13 of the first layer 11 and thesecond layer 12 are densified by compression to have an extremelysmaller thickness than the other part of the topsheet 1. A large numberof protrusions 15 are formed on the wearer's side of the topsheet 1 in aprescribed pattern, making a large number of depressions 14 on thejoints 13. These protrusions 15 and the depressions 14 provide an unevenprofile on the wearer's side of the topsheet 1.

[0022] The fiber aggregate forming the first layer 11 is nonwoven fabrichaving fusion-bonded fiber intersections P. The nonwoven fabric havingfusion bonded fiber intersections P may also contain fibers that are notfusion bonded to other fibers. The fiber aggregate forming the secondlayer 12 may be either nonwoven fabric having fusion bonded fiberintersections or nonwoven fabric with no fusion bonded fiberintersections.

[0023] Because the first layer 11 is made of nonwoven fabric havingfusion bonded fiber intersections P, the surface of the protrusions 15,which comes into contact with wearer's skin, suffers little fuzz that isliable to occur on nonwovens or fiber webs with no fusion bondedintersections. As a result, the topsheet 1 exhibits sufficient surfacestrength not to fuzz up while worn on friction with a wearer's body,giving little physical irritation to the skin and always assuringcomfort for a wearer.

[0024] The first layer 11 has an apparent thickness (t1) of 0.1 to 5 mm,preferably 0.1 to 3 mm, still preferably 0.5 to 2.0 mm. The second layer12 has an apparent thickness (t2) of 0.2 to 3 mm, preferably 0.3 to 3mm, still preferably 0.5 to 2.0 mm. The apparent thickness ratio of thefirst layer to the second layer, t1/t2, is 0.5 to 8, preferably 1 to 5,still preferably 1 to 3.

[0025] With an apparent thickness t1 less than 0.1 mm, the part capableof being deformed under wearing pressure applied is insufficient,resulting in a failure to give a fluffy and soft feel. With t1 exceeding5 mm, the liquid entering the protrusions must travel the increaseddistance to reach the second layer 12. As a result, the liquid is notsmoothly absorbed under low pressure applied to spoil the surface cleanimpression (whiteness) aimed by the present invention.

[0026] With an apparent thickness t2 smaller than 0.2 mm, the secondlayer 12 will have a non-uniform fiber distribution. The presentinvention is characterized by a fiber density difference between thefirst and the second layers, and the capillary force produced by such afiber density difference is made use of to develop such absorptivitythat does not allow liquid to remain on the surface. If there is anon-uniform fiber distribution, it would be difficult to make asufficiently dense structure, resulting in deviation from the objects ofthe invention. If the apparent thickness t2 is greater than 3 mm, therelatively dense structure of the second layer hinders liquid migrationto the absorbent member, and the second layer retains an increasedamount of liquid. This will reduce the hiding properties and theresistance to back flow of liquid.

[0027] If the apparent thickness ratio t1/t2 is smaller than 0.5, theproportion of the second layer's thickness in the total thickness of thetopsheet is too large, which will lead to insufficient hiding propertiesand insufficient prevention of liquid back flow. If it exceeds 8, theproportion of the first layer's thickness in the total thickness of thetopsheet is too large to make liquid smoothly migrate to the secondlayer which is denser and has a capillary force. It can follow thatliquid remains on the surface to give a wearer discomfort.

[0028] The height t3 (see FIG. 5A) of the protrusions is preferably 0.5to 5 mm, still preferably 0.5 to 3 mm, taking wearing comfort andabsorptivity into consideration. A height t3 smaller than 0.5 mm resultsin an increase in contact area with the skin, and some users may sufferfrom overhydration or a rash as a result. A height t3 larger than 5 mmis an increased distance the absorbed liquid must migrate to the secondlayer 12, and the liquid may fail to be absorbed smoothly under lowpressure applied.

[0029] The apparent thickness of the first and the second layers can bemeasured as follows. A 30 mm-side square cut out of a topsheet is cutalong a line substantially parallel with the longitudinal direction,namely, the fiber orientation direction (the machine direction) of thenonwoven fabric making the first layer, and passing through the joints13. A magnified photograph is taken of the cut area under a microscopeSZH10 supplied by Olympus Optical Co., Ltd. The real maximum thicknessof the first layer, calculated from the magnification, is taken as theapparent thickness t1 of the first layer. The thickness of the secondlayer at the same position of measuring the first layer thickness istaken as the apparent thickness t2 of the second layer. In other words,the thicknesses of the first and the second layers are measured on thesame straight line extending in the sheet thickness direction (see FIG.5A). The protrusion height t3 is the height of from the bottom of adepression to the apex of a protrusion as measured in the same manner asfor thicknesses t1 and t2.

[0030] In the topsheet 1, the second layer 12 has a higher fiber densitythan the first layer 11. The fiber density d1 of the first layer 11 is0.001 to 0.05 g/cm³, preferably 0.01 to 0.03/cm³, and the fiber densityd2 of the second layer 12 is 0.03 to 0.2 g/cm³, preferably 0.04 to 0.1g/cm³.

[0031] Where the fiber densities d1 and d2 fulfill the above-describedrequirements, liquid discharged on the topsheet 1 swiftly enters thefirst layer, and the liquid in the first layer 11 then smoothly migratesto the second layer 12 by virtue of the fiber density difference. As aresult, overhydration, skin troubles such as an itch and a rash, anddiscomfort which might occur due to liquid remaining on the surface ofthe topsheet can be prevented.

[0032] The first layer 11 and the second layer 12 are superposed on eachother and joined in parts. They are in contact with each other in notonly the joint areas 13 but other parts where the first layer 11 formsprotrusions. It is desirable that the first layer 11 and the secondlayer 12 are in contact with each other with no gap over the entire areaof each of the parts where the first layer 11 forms a protrusion.

[0033] If the fiber density dl is less than 0.001 g/cm³, the first layeris so sparse that the topsheet 1 lacks hiding properties (inclusive ofwhiteness). Moreover, the first layer 11 has a decreased number offusion bonded fiber intersections and is liable to fuzzing, which canimpair the wearing comfort. With a d1 more than 0.05 g/cm³, it isdifficult to make an effective density difference from the second layerenough to produce a sufficient capillary force.

[0034] If the fiber density d2 of the second layer is smaller than 0.03g/cm³, the second layer fails to have such a dense structure as todevelop a sufficient capillary force. As a result, liquid remains on thesurface, and the topsheet has reduced hiding properties (low cleanlinessfeel). The second layer with a density d2 exceeding 0.2 g/cm³ is toodense for securing smooth absorption, causing the liquid remainingproblem.

[0035] For making the sparse-dense structure of the first and secondlayers to develop a sufficient capillary force, the ratio of the fiberdensity d2 to the fiber density d1, d2/d1, is preferably 1.2 or higher,still preferably 3 to 10.

[0036] The fiber densities of the first layer 11 and the second layer 12are measured as follows. A 30 mm-side square cut out of a topsheetsample is cut along a line substantially parallel with the fiberorientation direction of the first layer, namely, the machine directionof the nonwoven fabric making the first layer, and passing through thejoints 13. The apparent thickness t1 (mm) of the first layer is measuredin the manner described supra.

[0037] The percent area shrinkage (A; %) of the sample is calculatedfrom the area of the first layer measured prior to shrinkage (beforejoining of the first layer and the second layer), represented by a₁×b₁,and the area of the first layer measured after shrinkage, represented bya₂×b₂, according to equation: A=[(a₁×b₁−a₂×b₂)/(a₁×b₁)]×100 (see FIG.5B). The basis weight P2 (g/m²) of the first layer is calculated fromthe area shrinkage A (%) and the basis weight P1 (g/m²) of the firstlayer before shrinkage (before joining of the first and the secondlayers) according to equation: P2=P1×100/(100−A). The fiber density d1(g/cm³) of the first layer is obtained from equation: d1=P2×({fraction(1/1000)})×(1/t1).

[0038] The fiber density d2 of the second layer 12 is obtained in thesame manner as for the d1. In the calculations, the apparent thicknesst2 of the second layer 12 is obtained in the same manner as for the t1.

[0039] To make the sparse-dense structure of the first and the secondlayers, it is preferred that the capillary rise h2 according to theKlemm method of the second layer 12 be higher than that (h1) of thefirst layer 11, i.e., h2>h1 and more preferred that the h2 to h1 ratio(h2/h1) be from 1.2 to 5. A capillary rise according to the Klemm methodwill hereinafter be referred to as a Klemm's capillary rise.

[0040] As a method for producing the difference between the first andsecond layers in Klemm's capillary rise, it is preferred to make thefiber density different between the two layers (i.e., the second layerhas a higher fiber density than the first layer), so that the secondlayer may exert a stronger capillary force than the first layer.

[0041] Other than the above method, it is effective to makehydrophilicity different between the two layers such that the secondlayer can have an increased Klemm's capillary rise by using ahydrophilizing agent having relatively higher hydrophilicity in thesecond layer. It is an effective manipulation, as a matter of course, tocombine making a fiber density difference and making a hydrophilicitydifference.

[0042] The Klemm's capillary rises of the first layer 11 and the secondlayer 12 are measured in accordance with JIS P8141 as follows.Measurement is carried out in the atmosphere satisfying the conditionsspecified in JIS P8111 (20° C., 65% RH). A 15 mm wide and 120 mm longstrip cut out of a topsheet sample is rapidly vertically soaked up to 5mm from its lower end in distilled water at 15 to 20° C. and allowed tostand for 10 minutes. The height (mm) of water having risen by capillarywas read at the middle of the width.

[0043] Klemm's capillary rise is usually represented by an average ofreadings in the machine direction and an average of readings in thetransverse direction of a sample. In the present invention, however,since the sample under test is nonwoven, the capillary rise is measuredonly in the longitudinal direction (generally the machine direction ofthe nonwoven) taking the fiber orientation direction into consideration,and an average of a plurality of specimens is obtained.

[0044] The process of producing the topsheet of the present inventionwill be described with particular reference to the topsheet 1. FIG. 2 isreferred to.

[0045] In this particular embodiment, a nonwoven fabric 11 a′ havingfusion bonded fiber intersections is treated with hot air into a bulkynonwoven fabric 11 a having an apparent density of 0.004 to 0.05 g/cm³and a thickness of 0.3 to 5 mm.

[0046] The nonwoven fabric 11 a′ is not particularly limited as long asit has fusion bonded fiber intersections. On being subjected to the hotair treatment, the nonwoven fabric 11 a′ becomes the bulky nonwovenfabric as a first layer-forming material 11 a. Such a firstlayer-forming material 11 a provides a first layer 11 which is resistantto fuzzing.

[0047] The nonwoven fabric 11 a′ is preferably made up of fiberscomprising thermoplastic polymers. Useful thermoplastic polymers includepolyolefins, such as polyethylene and polypropylene; polyesters, such aspolyethylene terephthalate; and polyamides. Conjugate fibers composed ofthese thermoplastic polymers, such as core-sheath conjugate fiber andside-by-side conjugate fiber, are also useful. It is preferred that thenonwoven fabric 11 a′ have substantially no thermal shrinkability orhave no thermal shrinkability at temperatures causing a secondlayer-forming material described infra to initiate shrinking.

[0048] Thermoplastic polymer fibers having been treated with anappropriate hydrophilizing agent are preferably used to give a firstlayer 11 that is wettable with blood and capable of drawing blood fromthe surface. Water-absorbing fibers (fibers capable of absorbing waterby themselves) such as cotton, rayon, and hydrophilized acrylic fibermay be used in place of, or in addition to, the fiber treated with ahydrophilizing agent. A difference of hydrophilicity between first andsecond layers can be produced by selecting the hydrophilicity or thecoating amount of the hydrophilizing agent or by adjusting the amount ofthe water-absorbing fiber to be incorporated.

[0049] The nonwoven fabric 11 a′ includes thermal bond nonwoven, airlaidnonwoven, air-through nonwoven, and melt-blown nonwoven.

[0050] The hot air treatment is carried out by, for example, (1)applying hot air to the surface of the nonwoven fabric 11 a′ or (2)forcing hot air through the thickness of the nonwoven fabric 11 a′. Themethod (2) is preferred for sufficient recovery of thickness by heat.

[0051] Where the bulky nonwoven fabric 11 a obtained by the hot airtreatment has an apparent density less than 0.004 g/cm³, the first layer11 has an insufficient surface strength, and the protrusions 15 areliable to fuzz, which can impair the comfort for a wearer. If theapparent density is higher than 0.05 g/cm³, the protrusions 15 tends tohave insufficient sparseness for developing desired absorbingperformance.

[0052] Where the bulky nonwoven fabric 11 a is thinner than 0.3 mm, gapstend to be formed between the first layer and the second layer onshrinking the second layer. If gaps are formed, liquid will be hinderedfrom migrating from the first to second layers and may remain on thesurface of the topsheet. With thicknesses greater than 5 mm, theproportion of the first layer's thickness in the total thickness of thetop sheet becomes too large on shrinking the second layer only to makeit difficult for liquid to migrate from the first to second layers. Itfollows that the topsheet fails to exhibit hiding properties and a dryfeel.

[0053] The bulky nonwoven fabric 11 a is superposed on a fiber aggregate12 a (a second layer-forming material), and the two layers are joined ina prescribed pattern. Any joining method that forms joints 13 where atleast the bulky nonwoven fabric 11 a has a smaller thickness than inother area is applicable. Thermal embossing or ultrasonic embossing is arecommended technique.

[0054] The pattern of the joints 13 includes spots, straight lines,curved lines (including continuous waves), lattices, and zigzags. Thespots may have arbitrary shapes, such as circles (dots), triangles, andrectangles.

[0055] On partly joining the bulky nonwoven fabric 11 a and the fiberaggregate 12 a in a prescribed pattern, there is formed a compositesheet 1′ consisting of the bulky nonwoven fabric 1 la and the fiberaggregate 12 a and having depressions on the joints 13 and lowprotrusions 15′ made of the bulky nonwoven fabric 11 a on the otherparts.

[0056] Where the first layer-forming material and the secondlayer-forming material are partially fusion-bonded by thermal orultrasonic embossing with an embossing surface (the peripheral surfaceof an embossing roll, for example) having embossing pins, a preferredpin density is 1 to 15 pins/cm², particularly 3 to 10 pins/cm², foravoiding absorption hindrance and ensuring smooth liquid penetration.After thermal shrinkage of the second layer, the number of the fusionbond joints 13 per cm² is preferably 1 to 30, still preferably 5 to 20,particularly preferably 5 to 10.

[0057] The fiber aggregate 12 a as the second layer-forming material ispreferably one that is capable of horizontally shrinking on beingsubjected to a prescribed treatment. A fiber aggregate which containsfibers capable of shrinkage when subjected to a prescribed treatment ispreferably used. From the standpoint of easy processing and easy controlon shrinkage, a fiber aggregate comprising thermally self-crimpingfibers or consisting essentially or solely of self-crimping fibers isparticularly preferred.

[0058] Self-crimping fibers are such that can be handled similarly toordinary fibers for nonwovens before heat application and, when heatedat a given temperature, crimp themselves in a helical form.Self-crimping fibers include conjugate fibers consisting of twothermoplastic polymers having different shrinkage characteristics in aneccentric core-sheath configuration or a side-by-side configuration.Examples of self-crimping conjugate fibers are given in JP-A-9-296325and Japanese Patent 2759331.

[0059] The fiber aggregate 12 a as the second layer-forming material maycontain fibers other than the fibers capable of shrinking when subjectedto a prescribed treatment. For example, the fiber aggregate 12 a maycontain water-absorbing fibers, such as rayon, cotton, and hydrophilicacrylic fiber.

[0060] Forms of the fiber aggregate 12 a as the second layer-formingmaterial include carded webs, thermal bond nonwovens, water needlednonwovens, needle punched nonwovens, solvent bonded nonwovens, spunbondnonwovens, and melt-blown nonwovens.

[0061] The fiber aggregate 12 a of the composite sheet 1′ is then madeto shrink in the horizontal direction (perpendicular to the thicknessdirection) by, for example, causing the fibers capable of shrinking whensubjected to a prescribed treatment to shrink. Upon the horizontalshrinkage of the fiber aggregate 12 a, the interfiber distance in theupper portion of the protrusions 15′ increases to reduce the apparentdensity in this portion. At the same time, the distance between adjacentjoints 13 reduces, and the apparent density of the fiber aggregate 12 abetween the joints 13 increases. The fiber aggregate 12 a is preferablyshrunken to an area shrinkage of 15 to 80%. There is thus produced thetopsheet 1 for absorbent articles.

[0062] A sanitary napkin as an embodiment of the absorbent articleaccording to the present invention will then be described with referenceto FIGS. 3 and 4. The sanitary napkin 10 comprises a liquid permeabletopsheet 1, a liquid impermeable backsheet 2, and a liquid retentiveabsorbent member 3 disposed between the two sheets.

[0063] The topsheet 1 and the backsheet 2 are joined at their extensionsfrom the periphery of the absorbent member 3 by known joining means,such as heat sealing and ultrasonic sealing, so that the absorbentmember 3 is held between the two sheets 1 and 2. A leak preventivegroove 4 surrounding the central portion (in the width and length) ofthe sanitary napkin 10 where blood is discharged is impressed from thetopsheet 1 side.

[0064] The topsheet of the sanitary napkin 10 is the topsheet 1 of theabove-described embodiment. The description about the topsheet 1 appliesto the topsheet used in the sanitary napkin 10.

[0065] The topsheet 1 in the absorbent article 10 shows athrough-thickness deformation of 0.03 to 0.3 mm/gf/cm², preferably 0.08to 0.3 mm/gf/cm², when compressed under a load of 10 gf/cm². With thethrough-thickness deformation less than 0.03 mm, the topsheet isincapable of sufficient deformation under low pressure applied, failingto provide a wearer with fluffy and soft feel. A topsheet with thedeformation more than 0.3 mm provides sufficient softness. However, sucha topsheet cannot be obtained without increasing the thicknessconsiderably, or such a fluffy topsheet allows its fibrous structure(interstices among fibers) to change so easily that a designed fibrousstructure cannot be retained. Either case can result in significantimpairment of the absorbing performance.

[0066] The through-thickness deformation per gf/cm² in compression under10 gf/cm² is obtained as follows. Measurement is made with a compressiontester KES-FB3, supplied by Katotec. The tester has a disk indenterhaving a compressing area of 2 cm². The disk indenter is verticallymoved to give a compression-recovery load to such a sample as fabric orfilm to obtain a compression load-compressive deformation hysteresisloop for the compression-recovery cycle, which furnishes compressiondata, such as the sample thickness, the compression work done, therecovery properties, and the like.

[0067] More concretely, a 2.5 cm-side square specimen is cut out of thetopsheet of an absorbent article 10 and set on KES-FB3. The diskindenter is moved down at a speed of 0.02 mm/sec to apply a compressionload up to 50 gf/cm², at which the manual return switch is pushed toswitch the downward movement to upward movement. The disk indenter islifted until the load decreases to zero. A hysteresis loop for thecompression-recovery cycle is plotted, from which the thickness t4 undera 10 gf/m² load in the process of compression is obtained. The thicknessunder a 0.5 gf/cm² load being taken as an initial thickness (t5), athickness reduction (t5−t4)(mm) is calculated, from which a thicknessdeformation per gf/cm² is calculated. The specimen to be measured is cutout of an appropriate region of the topsheet 1 so as to have protrusions15 all over the surface (the region containing the leak preventivegroove 4 or the peripheral seal should be avoided if possible) or tohave no or few collapsed protrusions 15. The specimen is preferably cutout of the region surrounded by the leak preventive groove 4,particularly the middle region of the width and the length of theabsorbent article 10.

[0068] The topsheet 1 alone used in the absorbent article 10 has asurface whiteness L1 (described later) of 60 or higher, preferably 70 orhigher, and a red plate hiding ratio (described later) of 40% or higher,preferably 45% or higher.

[0069] The difference between the surface whiteness La of the absorbentarticle (inclusive of the topsheet) before liquid absorption and thesurface whiteness Lb of the absorbent article (inclusive of thetopsheet) after absorbing 6 g of simulated blood, i.e., La-Lb, ispreferably 40 or smaller, and the Lb is preferably 60 or higher, stillpreferably 65 or higher.

[0070] The topsheet 1 which has an L value (L1) of 60 or higher is equalto conventional film type topsheets in color hiding performance andcapability of providing a clean impression (invisibility of the color ofliquid absorbed). The L value represents the capabilities of coveringblood having been absorbed and spread in the absorbent member. Thecloser the L value to 100, the whiter the sheet looks.

[0071] The absorbent article which has an Lb value of 60 or higher isequal to conventional absorbent articles having a film type topsheet incapabilities of providing a clean impression. The Lb value representsinvisibility of the blood stains of the topsheet in the central portionof the absorbent article. The higher the Lb value, the less the amountof the liquid remaining on the surface of the topsheet.

[0072] La-Lb differences of 40 or larger mean that blood remains in theskin layer of the topsheet and looks outstanding. A smaller differencebetween La (L value of the absorbent article before absorption) and Lb(L value of the absorbent article after absorption) means a smalleramount of liquid remaining in the skin layer, a cleaner impression, andsmaller possibility of causing overhydration and a skin rash.

[0073] The L value of the topsheet (L1), the red plate hiding ratio ofthe topsheet, and the L values of the absorbent article (inclusive ofthe topsheet) before absorption (La) and after absorption (Lb) aremeasured as follows.

[0074] Measurement of L Value of Topsheet (L1):

[0075] A color difference meter SZ-Σ80 supplied by Nippon DenshokuIndustries, Co., Ltd. is used after calibration with a white referenceplate. A light emitting pipe of 30 mm in diameter and a sample mount of30 mm in diameter are chosen. A specimen of the topsheet is put on theglass mount with its side to be measured (the side coming into contactwith a wearer) facing the light source. A specimen holder (black plate)attached to the instrument is placed on the specimen (opposite to theside to be measured). Five specimens cut out of different parts of asample are measured, and the readings are averaged to yield the L value(surface whiteness) of the sample.

[0076] Measurement of Red Plate Hiding Ratio:

[0077] Measurements are taken in the same manner as for the L value,except for replacing the black specimen holder with the red plateattached to the instrument. First of all, the red side of the red plate(with no specimen) is measured to prepare a spectral curve, and thereflectance Ra at a selected wavenumber of 500 cm⁻¹ is recorded. Then, aspecimen is placed between the glass and the red plate with the side tobe measured facing the light source. Five specimens cut out of differentparts of a sample are measured to obtain an average reflectance Rb at500 cm⁻¹. A red plate hiding ratio is calculated from equation:

Red plate hiding ratio (%)=[(Rb−Ra)/(100−Ra)]×100

[0078] Measurement of Surface Whiteness (La) of Absorbent Article BeforeAbsorption:

[0079] The surface whiteness of an absorbent article before absorption(La) is measured in the same manner as for the topsheet, except that theabsorbent article (product) is placed on the glass mount with thetopsheet side facing the light source.

[0080] Measurement of Surface Whiteness (Lb) of Absorbent Article AfterAbsorption:

[0081] Simulated blood is prepared as follows. In a 2 liter beaker isput 1500 g of ion-exchanged water, and 5.3 g of sodium carboxymethylcellulose (CMC-Na, available from Kanto Kagaku K.K.) is dissolvedtherein by stirring with a magnetic stirrer. Separately, 556 g ofion-exchanged water is put into a 1 liter beaker, and 27.0 g of sodiumchloride and 12 g of sodium hydrogencarbonate (NaHCO₂, available fromKanto Kagaku) are dissolved therein by stirring with a stirrer. Theresulting two solutions and 900 g of glycerin are mixed up by stirringin a 3 liter beaker.

[0082] To the mixture are added 15 ml of aqueous solution of nonionicsurfactant “Emulgen 935” (available from Kao Corp.) having aconcentration of 1 g/L (surfactant/water) and 0.3 g of Red #2 (producedby Daiwa Kasei K.K. and available from Aisen K.K. and Hodogaya ChemicalCo., Ltd.), followed by stirring. The mixture is filtered by suctionthrough a glass filter to prepare simulated blood.

[0083] Simulated blood may also be prepared by using other nonionicsurfactants than the aforementioned one to obtain the same results.However, the amount of surfactant should be adjusted such that thecontact angle of the simulated blood falls within the range of 35-40°with respect to the surface of a glass plate. The contact angle isobtained by measuring a contact angle of simulated blood with respect tothe glass surface (cleansed by ethanol) with use of a contact anglemeasuring apparatus (manufactured by KYOWA INTERFACE SCIENCE CO., LTD.,FACE Contact Angle Meter CA-A type).

[0084] Six grams of the simulated blood put in a 10 ml beaker iscarefully poured through a pouring tool on the topsheet side of anabsorbent article the surface whiteness of which has been measured. Thepouring tool consists of an acrylic plate (100 mm×200 mm×8 mm (t))having a through-hole of 10 mm in diameter at the center thereof and ahollow cylinder made of a smaller-diametered cylinder of 10 mm in innerdiameter and a larger-diametered cylinder of 22 mm in inner diameterconcentrically connected in series via a joint tapered at an angle of45° with the axis of the cylinders, the end of the smaller-diameteredcylinder being concentrically joined to the through-hole of the acrylicplate. The pouring tool is placed on the absorbent article with itsthrough-hole at the center of the length and width of the absorbentarticle. Simulated blood (6 g) is poured into the opening of thelarger-diametered cylinder over about 5 seconds and discharged from thehole of the plate. After the pouring, the absorbent article is allowedto stand for 120 seconds, and the surface whiteness Lb is measured inthe same manner as for the La value (L value before absorption).

[0085] The material of the backsheet 2 and the absorbent member 3constituting the absorbent article 10 can be of any materials that haveconventionally been employed in absorbent articles such as disposablediapers. For example, the absorbent member 3 can be made of a fiberaggregate and a superabsorbent polymer. The fiber aggregate includesnonwoven fabrics and fiber webs. The superabsorbent polymer is used asheld, e.g., in the interstices of fibers of the fiber aggregate orbetween layers of a multilayer structure made of fiber aggregates.

[0086] The present invention is not limited to the above-describedembodiments. For example, the topsheet which can be used in theabsorbent article as claimed in the present invention is not limited toone that satisfies all the requirements of the topsheet as claimed inthe present invention, and the topsheet for absorbent article as claimedin the present invention is not limited to one that satisfies all therequirements of the topsheet which can be used in the absorbent articleas claimed in the present invention.

[0087] The absorbent articles according to the present invention includenot only sanitary napkins described supra but other products having aliquid permeable topsheet, a liquid impermeable backsheet, and anabsorbent member interposed therebetween which are adapted to absorb andretain liquid body waste such as urine and menstrual blood, such asincontinence pads, panty liners, and disposable diapers.

EXAMPLE 1

[0088] The present invention will now be illustrated in greater detailwith reference to Examples. Unless otherwise noted, all the percents andratios are by weight.

[0089] Preparation of Topsheet:

[0090] Thermally fusion bondable core-sheath conjugate fiber (2.2dtex×51 mm) consisting of a polyethylene terephthalate core and apolyethylene sheath available from Daiwabo Co., Ltd. was carded into aweb and heat treated at 120° C. to fusion bond the fiber intersectionsto prepare nonwoven fabric having a basis weight of 15 g/m². Thenonwoven fabric was subjected to hot air treatment at 70° C. to obtainbulky nonwoven fabric (first layer-forming material) having a thicknessof 1 mm and an apparent density of 0.025 g/cm³.

[0091] Separately, helically self-crimping fiber CPP (2.2 dtex×51 mm,available from Daiwabo Co., Ltd.) was carded into a web having a basisweight of 35 g/m² (second layer-forming material).

[0092] The first layer-forming material and the second layer-formingmaterial were superposed on each other and partly joined together byultrasonic embossing using an embossing plate having standing pins in adot pattern. The dot pattern of the standing pins is repetition (exceptfor the edges of the embossing roll) of a unit pattern consisting of acentral pin C, a pair of pins arranged on a straight line parallel tothe longitudinal direction (MD) and passing through the center of thepin C at a center-to-center distance of about 7 mm from the pin C, apair of pins arranged on a straight line parallel to the width direction(CD) and passing through the center of the pin C at a center-to-centerdistance of about 7 mm from the pin C, and two pairs of pins eacharranged on a straight line passing through the center of the pin C andmaking an angle of 45° with the MD and the CD at a center-to-centerdistance of about 5 mm from the pin C.

[0093] The resulting composite sheet was heated at 130° C. for about 1to 10 minutes to is shrink the second layer-forming material in thehorizontal direction to an area shrinkage of 56% to obtain a topsheethaving a large number of protrusions 15 as shown in FIG. 1.

[0094] The resulting topsheet was examined to reveal that the fibersconstituting the side wall 15 a of each protrusion 15 and nearby fiberswere oriented almost in parallel with each other along the curved planebetween the apex 15 b and the joint 13. The resulting topsheet wasexamined for apparent thickness t1 of the first layer, apparentthickness t2 of the second layer, fiber density d1 of the first layer,fiber density d2 of the second layer, Klemm's capillary rise hl of thefirst layer, Klemm's capillary rise h2 of the second layer, andthrough-thickness deformation per gf/cm² in compression under a 10gf/cm² load. The results obtained are shown in Table 1 below.

[0095] Production of Absorbent Article:

[0096] The topsheet prepared above and a polyethylene film backsheet(one used in Lorie UN-f-11 Sarasara Cushion Slim with no wings,available from Kao Corp.) were set on the upper and the lower sides,respectively, of an absorbent member (thickness: 4.5 mm; an aggregatemade of 200 g/m² of fluff pulp and 40 g/m² of absorbent polymer (acrylicacid-sodium acrylate copolymer) and wrapped in absorbent paper having abasis weight of 16 g/m²). A leak preventive groove 4 and peripheral seal5 were formed to make a sanitary napkin shown in FIGS. 3 and 4.

[0097] Surface whitenesses L1 of the topsheet alone, La of the absorbentarticle before absorption, and Lb of the absorbent article afterabsorption were measured. The results are shown in Table 1.

EXAMPLE 2

[0098] A topsheet was prepared in the same manner as in Example 1,except that a bulky nonwoven fabric having a thickness of 0.9 mm, anapparent density of 0.013 g/cm³, and a basis weight of 12 g/m² wasprepared as a first layer-forming material and that the secondlayer-forming web partly joined with the bulky nonwoven fabric wasshrunken at an area shrinkage of 30%.

EXAMPLE 3

[0099] A topsheet was prepared in the same manner as in Example 2,except that the percent area shrinkage was changed to 15%.

EXAMPLE 4

[0100] Helically self-crimping fiber CPP (2.2 dtex×51 mm, available fromDaiwabo Co., Ltd.) and thermally fusion bondable core-sheath conjugatefiber (2.2 dtex×51 mm) consisting of a polyethylene terephthalate coreand a polyethylene sheath available from Daiwabo Co., Ltd. were mixed ata weight ratio of 50:50 and carded into a web having a basis weight of35 g/m².

[0101] A topsheet was prepared in the same manner as in Example 1,except for using the resulting web as a second layer-forming material.

COMPARATIVE EXAMPLE 1

[0102] A topsheet was prepared in the same manner as in Example 1,except for using, as a first layer-forming material, a web having abasis weight of 15 g/m² prepared by carding the same fiber as used inExample 1 (having no fusion-bonded fiber intersections).

COMPARATIVE EXAMPLE 2

[0103] A topsheet was prepared in the same manner as in Example 1,except for using, as a first layer-forming material, spunbond nonwovenfabric made solely of polypropylene fiber and having a basis weight of12 g/m².

COMPARATIVE EXAMPLE 3

[0104] The topsheet used in Lorie UN-f-11 Sarasara Cushion Slim (with nowings), available from Kao Corp., was examined.

COMPARATIVE EXAMPLE 4

[0105] The topsheet used in Lorie DR-h-114 Dry-up Mesh Regular,available from Kao Corp., was examined.

[0106] The topsheet of Comparative Example 3 is made of perforatednonwoven fabric of core-sheath conjugate fiber consisting of apolyethylene telephthalate core and a polyethylene sheath and thenonwoven fabric is provided with 10 to 15 pores/cm² of about 0.8 to 1 mmin diameter. The topsheet of Comparative Example 4 is made of perforatedpolyethylene film.

[0107] Evaluation of Absorbing Performance (Blood Hiding Properties):

[0108] Sanitary napkins were produced under equal conditions with thesame materials, except for using each of the topsheets prepared inExamples 1 to 4 and Comparative Examples 1, 2 and 4. Twelve females wereasked to actually use the sanitary napkins and compare them withreference sanitary napkins Lorie UN-f-11 Sarasara Cushion Slim (with nowings) for blood hiding properties. Ten persons out of the twelve judgedthat the topsheet of Example 1 made blood more obscure than that of thereference article (supported the product of the present invention).

[0109] Evaluation of Comfort in Use:

[0110] The 12 females were also asked to evaluate the soft feel of thetopsheet while worn in the same actual testing. Five out of twelvejudged that the topsheet of Example 1 was softer than that of thereference article, and the rest judged these topsheets equal insoftness.

[0111] Organoleptic Test on Fuzz:

[0112] Twenty females evaluated the topsheets of Examples 1 to 4 andComparative Examples 1 to 4 by appearance and feel to the touch. As aresult, 16 out of 20 (80%) judged the topsheet of Comparative Example 1no good because of fuzz, and all judged that fuzz, if any, of the othertopsheets was not such to care about. TABLE 1 Example ComparativeExample 1 2 3 4 1 2 3 4 Topsheet: Apparent Thickness t1 2.00 1.40 0.601.50 2.30 0.15 0.42 0.57 (mm) t2 1.00 0.80 1.10 1.50 1.17 1.18 — — t1/t22.0 1.8 0.6 1.0 2.0 0.1 — — Fiber Density (g/cm³) d1 0.017 0.012 0.0240.020 0.014 0.080 0.060 — d2 0.080 0.063 0.037 0.047 0.086 0.086 — —d2/d1 4.7 5.3 1.5 2.4 6.1 1.1 — — Klemm's Capillary h1 6 6 6 6 4 6 6 —Rise (mm) h2 14 12 9 13 14 13 — — Through-thickness Deformation at 0.080.08 0.06 0.14 0.16 0.12 0.05 0.01 10 gf/cm²(mm/gf/cm²) Whiteness L1 8069 62 77 80 60 62 75 Red Plate Hiding Ratio (%) 66 49 42 63 65 40 34 56Height t3 of Protrusion (mm) 2.60 2.00 1.30 2.70 3.00 1.85 — — AbsorbentArticle: Surface Whiteness La 96 95 95 97 95 96 96 97 Lb 74 70 65 76 7454 60 74 La − Lb 22 25 30 21 21 42 36 23 Organoleptic Test on Fuzz (NG 00 0 0 80 0 0 0 Ratio) (%)

[0113] It is seen from the results of evaluation in Examples andComparative Examples that the topsheet according to the presentinvention is excellent in both absorbing performance and surfacesoftness. That is, the topsheet of the invention makes liquid waste suchas menstrual blood or urine quickly migrate to the absorbent member andfeels soft (cushioning and fluffy) on the side in contact with a wearer,giving little irritation to the skin. In particular, protrusions of thetopsheet the first layer of which is made of nonwoven fabric havingfusion bonded fiber intersections have a reduced fiber density andimproved resistance against fuzzing.

[0114] It has also been proved that the absorbent article according tothe present invention gives a user a clean impression because of thetopsheet's capability of making the color of discharged liquid wastesuch as menstrual blood or urine obscure, has excellent softness on thewearer's side to prevent an itch, a rash or discomfort due to physicalirritation, and assures a wearer an excellent comfort while being worn.

[0115] The topsheet for an absorbent article according to the presentinvention has not only absorbing performance for smoothly transferringliquid body waste, e.g., menstrual blood or urine, to an underlyingabsorbent member but surface characteristics such that the surfacethereof in contact with wearer's skin is soft enough not to cause skinirritation. Therefore, it prevents an itch, a rash or discomfort due tooverhydration or irritation and assures a wearer an excellent comfort (acushioning feel) while being worn.

[0116] The absorbent article according to the present invention gives auser a clean impression because of the topsheet's capability of makingthe color of discharged liquid waste such as menstrual blood or urineobscure, has excellent softness on the wearer's side to prevent an itch,a rash or discomfort due to physical irritation, and assures a wearer anexcellent comfort (a cushioning feel) while being worn.

[0117] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

[0118] This application claims the priority of Japanese PatentApplication Nos. 2001-398779 filed Dec. 28, 2001 and 2002-301297 filedOct. 16, 2002, which are incorporated herein by reference.

What is claimed is:
 1. A topsheet for an absorbent article comprising a first layer disposed on the side of a wearer and a second layer disposed on the side of an absorbent member, the first layer and the second layer being partly joined together, and having protrusions and depressions on the side of a wearer, wherein said first layer and said second layer each comprise a fiber aggregate, said first layer has fusion-bonded fiber intersections, said first layer has an apparent thickness (t1) of 0.1 to 5 mm, said second layer has an apparent thickness (t2) of 0.2 to 3 mm, the apparent thickness ratio of said first layer to said second layer (t1/t2) is 0.5 to 8, said first layer has a fiber density (d1) of 0.001 to 0.05 g/cm³, said second layer has a fiber density (d2) of 0.03 to 0.2 g/cm³, and the fiber density (d2) of said second layer is higher than the fiber density (d1) of said first layer.
 2. The topsheet according to claim 1, wherein said first layer and said second layer are in contact with each other in not only the joint areas but other parts.
 3. The topsheet according to claim 1, wherein the ratio of the fiber density d2 of said second layer to the fiber density dl of said first layer, d2/d1, is 1.2 or higher.
 4. The topsheet according to claim 1, wherein said second layer has a higher capillary rise according to the Klemm method than said first layer.
 5. A process of producing a topsheet for an absorbent article according to claim 1, which comprises subjecting a nonwoven fabric having fusion-bonded fiber intersections to a hot air treatment to form a bulky nonwoven fabric having an apparent density of 0.004 to 0.05 g/cm³ and a thickness of 0.3 to 5 mm, superposing the bulky nonwoven fabric as a first layer-forming material and a fiber aggregate as a second layer-forming material on each other, partly joining the first layer-forming material and the second layer-forming material to form a composite sheet, and shrinking the second layer-forming material in the horizontal direction.
 6. The process of producing a topsheet for an absorbent article according to claim 5, wherein said fiber aggregate as a second layer-forming material is a fiber aggregate containing fiber capable of shrinking when subjected to a treatment, and the step of shrinking the second layer-forming material is carried out by said treatment.
 7. The process of producing a topsheet for an absorbent article according to claim 6, wherein said fiber capable of shrinking when subjected to a treatment is self-crimping fiber capable of crimping itself when subjected to a heat treatment.
 8. An absorbent article comprising a liquid permeable topsheet, a liquid impermeable backsheet, and a liquid retentive absorbent member interposed between the topsheet and the backsheet, wherein: said topsheet comprises a first layer disposed on the side of a wearer and a second layer disposed on the side of an absorbent member and has protrusions and depressions on the side of a wearer, said first layer comprises a fiber aggregate having fusion-bonded fiber intersections, said first layer has an apparent thickness (t1) of 0.1 to 5 mm, said second layer has an apparent thickness (t2) of 0.2 to 3 mm, the apparent thickness ratio of said first layer to said second layer (t1/t2) is 0.5 to 8, said topsheet shows a through-thickness deformation of 0.03 to 0.3 mm per gf/cm² when compressed under a load of 10 gf/cm², and said topsheet has a surface whiteness of 60 or higher in terms of L value and a red plate hiding ratio of 40% or higher.
 9. The absorbent article according to claim 8, wherein the difference between the surface whiteness La, in terms of L value, of the absorbent article before liquid absorption and the surface whiteness Lb, in terms of L value, of the absorbent article after absorbing 6 g of simulated blood, La-Lb, is 40 or smaller, and the Lb is 60 or higher. 